deduction of account balance from mobile

I am a reliance mobile customer. As soon as I switch on the mobile my balance is deducted from the mobile without any intimation. Rs 15-20 is deducted regularly. I would like to know why the deduction of amount is taking place.
Please look forward to it and return the amount as soon as possible or I will switch to another company. I have called the customer care many times and they are not giving satisfactory response. My no is – 07828686575